Compositions that can absorb organic liquids, especially from aqueous mixtures, are of considerable interest. Oil-absorbent compositions are described in U.S. Pat. No. 3,520,806. An alkylated styrene monomer, such as tert-butylstyrene, is polymerized in the presence of a free-radical initiator and a polyethylenically unsaturated compound such as divinylbenzene. Crosslinking from the difunctional monomer makes the composition insoluble in the organic liquid. When the polymer composition and organic liquid are combined, the polymer swells with many times its weight of the organic liquid, but remains insoluble.
Polymeric resins containing phosphonic acid groups are known in the art. Examples include styrene/1-phenylvinylphosphonic acid copolymers (Plast. Massy, No. 8 (1966) 24), crosslinked vinyl phosphonate copolymers (U.S. Pat. No. 3,726,839), and styrenic polymers that contain pendent phosphonate ester groups (J. Polym. Sci. A, Polym. Chem. Ed. 28 (1990) 227; 27 (1989) 3985). The reaction products of polymeric resins containing phosphonic acid groups with di- or polyamines and the use of such resins as absorbents for organic liquids have not been previously disclosed.
Previously known absorbents for organic liquids--typically the crosslinked alkylated styrene polymers described above--have limited utility because they are generally non-processable solids. A processable solid, i.e., one that can be thermally processed or dissolved in a solvent, is desirable because it can be processed before use into the most effective form (e.g., fiber, particle, solid shape) for a specific end use. A liquid absorbent or a solid absorbent that can be dissolved and used in liquid form would be preferred for some applications.
Another disadvantage of organic-liquid absorbents known in the art is that the spent absorbent, which is typically gel-like when swollen with an organic liquid, is not easy to process or transport. In addition, the organic liquid and absorbent polymer are not easily recovered from the spent absorbent, so the spent absorbent is typically buried or incinerated.
An ideal absorbent could be: (a) handled and used as either a processable solid or liquid, (b) transformed, when spent, from a gel to a pumpable, stirrable liquid, and (c) recycled to give back the organic liquid and a useful absorbent material, thus eliminating the need for costly waste treatment and disposal.